Can I reuse wire for larger array?

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rgk1
rgk1 Solar Expert Posts: 135 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
I am moving my current array to a new location and now is the time to change wire if required for future upgrade. Currently have 4 series connected 12 volt panels with 10awg direct burial wire run underground in 1" conduit and about 50' to charge controller input. In the future I plan to upgrade to 4 larger panels that have yet to be determined.  When the time comes I will pick from whatever is common at the time.  Seems most larger panels are in the mid 30's on voltage and around 9 amps. The question is, if new panels are wired 2 series then parallel giving roughly 70 volts and 20amps, is the current wire I already have acceptable?  The distance for new array will be 35-40' from combiner to CC.
4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Estragon
    Estragon Registered Users Posts: 4,503 ✭✭✭✭✭
    #2
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=70&phase=dc&noofconductor=1&distance=40&distanceunit=feet&amperes=20&x=114&y=26

    Looks okay to me, assuming 12 or 24v system voltage.  2 in series might be a bit low for 48v, especially if the bank gets cold.
    Off-grid.  
    Main system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #3
    Will be keeping system at 24v.  Part of my revamp is to move batteries out of hot shed and into an outdoor enclosure in the shade. Have rust forming on metal things in the shed and think the batteries being in there is partly to blame. 
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
    The 10 AWG is acceptable however if planning upgrading in the future  it is the perfect opportunity to increase the gauge, the current system will  benifit as well until upgrading, over sizing has no negative impact. The labor involved in replacement at a later date will exceed the costs, and or physical expenditure of doing it twice, always think ahead.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #5
    Estragon, I did see and use that very calculator you linked to.  Voltage drop looked acceptable, but made me question amp vs wire gauge.  It is a bit fuzzy to me when you start taking things into account such as insulation type, in/out of conduit and such when figuring current carrying capacity.  I didnt see the amp chart till I looked at it again on your link. Looks like 30 amp capacity on the low side so I guess I should be good.  mcgivor has a good point too though.  Just wasnt looking forward to navigating the wire-crowded Midnite DC box with bigger wire. Decisions, decisions.  Thanks for the help and always great advice from this forum!
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #6
    Using a larger gauge to span the longest distance then transpose to a lighter gauge at the termination end, will reduce overall voltage drop. The overcurrent protection device would however be limited to the smallest gauge in the entire circuit. This would allow future expansion with just the replacement of the short termination should the need arise.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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